A well-known semiconductor memory component is a random access memory (RAM). RAM permits repeated read and write operations on memory elements. Typically, RAM memory elements are volatile, in that stored data is lost once the power source is disconnected or removed. Non-limiting examples of RAM devices which contain such memory elements include dynamic random access memory (DRAM), synchronized dynamic random access memory (SDRAM) and static random access memory (SRAM). DRAM's and SDRAM's typically store data in capacitors which require periodic refreshing to maintain the stored data.
Recently, resistance variable memory elements have been investigated for suitability as semi-volatile and non-volatile random access memory elements. A class of such devices include an insulating material formed of a chalcogenide glass disposed between two electrodes. A conductive material is incorporated into the material. The resistance of the material can be changed between high and low resistance states by application of suitable voltages across the memory element. D. D. Thornburg has discussed polarization of arsenic triselenide in an electric field. For instance, the polarization of arsenic triselenide allows the memory device to switch between different memory states. See Thornburg, D. D., Memory Switching in Amorphous Arsenic Triselenide, J. NON-CRYST. SOLIDS 11 (1972), at 113–120; Thornburg, D. D. and White, R. M., Electric Field Enhanced Phase Separation and Memory Switching in Amorphous Arsenic Triselenide, J. APPL. PHYS. (1972), at 4609–4612.
When set in a particular resistance state, the particular resistance state of the memory element will remain intact for minutes, hours, or longer even after the voltage potentials are removed. Such a device can function, for example, as a semi or non-volatile resistance variable memory element having two resistance states, which in turn can define two logic states.